Bridge Problem
Bridge Problem
(OP)
I'm working on remedial works to an existing bridge an Africa. It looks like it was constructed in the 1960's. Anyway I don't have any details on the existing design. I tried to analyse the bridge for the existing spans with current truck loading etc and it comes no where near to working although large trucks use it every day.
I have to provide two new carriageways underneath the bridge each at 5.0m wide. See attached existing and proposed.
I measured the beam on site and worked out a rough load based upon a moment capacity for the existing span. My new support arrangement will not result in any larger moments. Based upon this load. My brief is to ensure we don't weaken the existing structure.
I have analysed the new structure as two cantilevers at the ends with the existing splice connections taking no moment. This is under uniform loading. I know non uniform loading will occur. I'm concerned about load transfer across the splice. Anyone got any simple ideas to resolve this. Materails and skilled labour are very rare. I do have some old beams 500mm deep but only 2.0m long. I'm thinking of bolted these to the underside of the existing beams across the splice.
Any recommendations?
I have to provide two new carriageways underneath the bridge each at 5.0m wide. See attached existing and proposed.
I measured the beam on site and worked out a rough load based upon a moment capacity for the existing span. My new support arrangement will not result in any larger moments. Based upon this load. My brief is to ensure we don't weaken the existing structure.
I have analysed the new structure as two cantilevers at the ends with the existing splice connections taking no moment. This is under uniform loading. I know non uniform loading will occur. I'm concerned about load transfer across the splice. Anyone got any simple ideas to resolve this. Materails and skilled labour are very rare. I do have some old beams 500mm deep but only 2.0m long. I'm thinking of bolted these to the underside of the existing beams across the splice.
Any recommendations?
Kieran






RE: Bridge Problem
Kieran
RE: Bridge Problem
Kieran
RE: Bridge Problem
Are the twelve existing bolts adequate to carry shear? Can the outer ends of the 3410 span be anchored down to resist uplift when a heavy concentration is placed on the splice point?
Could you replace the existing bolts with larger, stronger bolts, i.e. 3/4" A325 bolts to 1" A490 bolts?
BA
RE: Bridge Problem
The outer ends of the 3410 span will be anchored down to resist uplift. I also need to do a little more investigation into the size of the end abutments and will apply a ballast if necessary.
With regards to the beams underneath, the only traffic using this will be haulage trucks from a mine. I guess they don't care what it looks like. I also realised the 500mm beams will restrict headroom so i may have to cut them in half and weld a plate to the cut end.
Kieran
RE: Bridge Problem
Take a look at page 22 of the attachment. Perhaps this is what your thinking? If your strucutre is modelled with pins, the pin & hanger retrofit shown maintains that condition. If you can make things work with the materials you have the capacity of the splice becomes a non-issue.
RE: Bridge Problem
Kieran
RE: Bridge Problem
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I think a moment connection is a better way to go. Hopefully, you can find a qualified welder. Doing a full pen groove weld in the field will be difficult.
RE: Bridge Problem
Kieran
RE: Bridge Problem